1 files changed, 96 insertions, 0 deletions
diff --git a/src/test/modules/test_ginpostinglist/test_ginpostinglist.c b/src/test/modules/test_ginpostinglist/test_ginpostinglist.c
new file mode 100644
index 0000000..9a23009
--- /dev/null
+++ b/src/test/modules/test_ginpostinglist/test_ginpostinglist.c
@@ -0,0 +1,96 @@
+/*--------------------------------------------------------------------------
+ *
+ * test_ginpostinglist.c
+ *		Test varbyte-encoding in ginpostinglist.c
+ *
+ * Copyright (c) 2019-2022, PostgreSQL Global Development Group
+ *
+ * IDENTIFICATION
+ *		src/test/modules/test_ginpostinglist/test_ginpostinglist.c
+ *
+ * -------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "access/gin_private.h"
+#include "access/ginblock.h"
+#include "access/htup_details.h"
+#include "fmgr.h"
+
+PG_MODULE_MAGIC;
+
+PG_FUNCTION_INFO_V1(test_ginpostinglist);
+
+/*
+ * Encodes a pair of TIDs, and decodes it back. The first TID is always
+ * (0, 1), the second one is formed from the blk/off arguments. The 'maxsize'
+ * argument is passed to ginCompressPostingList(); it can be used to test the
+ * overflow checks.
+ *
+ * The reason that we test a pair, instead of just a single TID, is that
+ * the GinPostingList stores the first TID as is, and the varbyte-encoding
+ * is only used for the deltas between TIDs. So testing a single TID would
+ * not exercise the varbyte encoding at all.
+ *
+ * This function prints NOTICEs to describe what is tested, and how large the
+ * resulting GinPostingList is. Any incorrect results, e.g. if the encode +
+ * decode round trip doesn't return the original input, are reported as
+ * ERRORs.
+ */
+static void
+test_itemptr_pair(BlockNumber blk, OffsetNumber off, int maxsize)
+{
+	ItemPointerData orig_itemptrs[2];
+	ItemPointer decoded_itemptrs;
+	GinPostingList *pl;
+	int			nwritten;
+	int			ndecoded;
+
+	elog(NOTICE, "testing with (%u, %d), (%u, %d), max %d bytes",
+		 0, 1, blk, off, maxsize);
+	ItemPointerSet(&orig_itemptrs[0], 0, 1);
+	ItemPointerSet(&orig_itemptrs[1], blk, off);
+
+	/* Encode, and decode it back */
+	pl = ginCompressPostingList(orig_itemptrs, 2, maxsize, &nwritten);
+	elog(NOTICE, "encoded %d item pointers to %zu bytes",
+		 nwritten, SizeOfGinPostingList(pl));
+
+	if (SizeOfGinPostingList(pl) > maxsize)
+		elog(ERROR, "overflow: result was %zu bytes, max %d",
+			 SizeOfGinPostingList(pl), maxsize);
+
+	decoded_itemptrs = ginPostingListDecode(pl, &ndecoded);
+	if (nwritten != ndecoded)
+		elog(NOTICE, "encoded %d itemptrs, %d came back", nwritten, ndecoded);
+
+	/* Check the result */
+	if (!ItemPointerEquals(&orig_itemptrs[0], &decoded_itemptrs[0]))
+		elog(ERROR, "mismatch on first itemptr: (%u, %d) vs (%u, %d)",
+			 0, 1,
+			 ItemPointerGetBlockNumber(&decoded_itemptrs[0]),
+			 ItemPointerGetOffsetNumber(&decoded_itemptrs[0]));
+
+	if (ndecoded == 2 &&
+		!ItemPointerEquals(&orig_itemptrs[0], &decoded_itemptrs[0]))
+	{
+		elog(ERROR, "mismatch on second itemptr: (%u, %d) vs (%u, %d)",
+			 0, 1,
+			 ItemPointerGetBlockNumber(&decoded_itemptrs[0]),
+			 ItemPointerGetOffsetNumber(&decoded_itemptrs[0]));
+	}
+}
+
+/*
+ * SQL-callable entry point to perform all tests.
+ */
+Datum
+test_ginpostinglist(PG_FUNCTION_ARGS)
+{
+	test_itemptr_pair(0, 2, 14);
+	test_itemptr_pair(0, MaxHeapTuplesPerPage, 14);
+	test_itemptr_pair(MaxBlockNumber, MaxHeapTuplesPerPage, 14);
+	test_itemptr_pair(MaxBlockNumber, MaxHeapTuplesPerPage, 16);
+
+	PG_RETURN_VOID();
+}